This invention relates to a process for the manufacture of yarn and more particularly to a process for manufacturing a balanced yarn formed of a synthetic, thermoplastic material.
In order to provide fabric products exhibiting desirable properties, e.g., high stretch characteristics with retentivity of shape despite washing, dry cleaning, etc., yarn texturizing processes have been developed for treating the yarns of which these fabric products are to be made.
A conventional method of texturizing thermoplastic yarns generally utilizes twisting and heat-setting techniques. Essentially, a measured high twist is imparted to the yarn (the amount of twist depending upon the denier or thickness of the yarn), the yarn is heat-set in the twisted condition in a high pressure steam autoclave for a predetermined amount of time, and finally the yarn is reversely twisted to a predetermined amount. As a result, the torque or tendency to twist back to its heat-set condition causes the filaments of the yarn to bulk up into a spring-like condition which results in a desirable high-stretch yarn.
Unfortunately, after this conventional texturizing technique is applied, the yarn has a tendency to kink when being knitted into fabric products. This tendency results from the torque retained in the yarn which gives it the beneficial high-stretch and bulk characteristics. Such kinking prevents the effective use of such yarn for knitted goods since these goods tend to become distorted due to the relatively high degree of kinking. Such kinking is particularly disadvantageous for use in sewing, where it is necessary for the yarn to pass through needles, with controlled tensions.
Several methods of reducing torque in texturized yarn are currently known. For example, one common method of mitigating the kinking in yarn is to combine the yarn (having for example an S-twist) with another yarn treated in the same manner, but twisted in an opposite direction (i.e., a Z-twist), to produce a multi-ply yarn. The yarns so plied, respectively having an S-twist and a Z-twist, compensate one another so that the resultant yarn has practically no directional torque. This process is disadvantageous in that two separate processes must be performed on two individual strands of yarn of one-half the denier desired in the finished yarn.
Another method of reducing torque without plying comprises high-twisting the texturized yarn in a direction opposite to that of the first high-twisting, heat-setting it and untwisting the same. This process is advantageous in that, because it does not use a plying technique, a fine denier product can be obtained. However, this process has not been found to be completely advantageous since there remains enough residual torque in the yarn so as to make the yarn unsuitable for use in sewing.